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The sensors themselves can be way out of wack and not cause an alarm, if you suspect this, then you should pull the sensors out and let them sit in a cold water bath[/U] along with an accurate thermometer. These sensors are in the refrigerant flow so you have to pump the evaporator refrigerant from the king valve to the compressor into the condenser and if you not sure of yourself doing this find someone who knows this procedure.

I agree that the sensors should not be put in water unless you want to introduce moisture into the chiller.

There is no reason the chiller can't be pumped down to replace the sensors. Hook up your gauges and have your hand on the disconnect and make sure it doesn't go into a vacuum. It is not necessary to pull the entire charge just to change the sensors. Pump it down to 20 PSI and change them on the fly.

I have replaced a lot of RTAA suction temp. sensors and have yet to get sprayed with oil. Not saying it can't happen, but hasn't happened to me yet.

You got me curious. I usually just isolate the compressor and recover residual then take it out. But I am pretty sure I have always had oil come out steadily. If there ain't some oil that comes out I would be worried. You are talking about comp suction temp sensor and not the sat evap temp sensor?

Refrigerant sensors

Cowpoke- I generally leave just a little (2-4) pounds of pressure and have a new sensor already made up (compression ring on the sensor) so I can pull the old sensor out and push the new sensor in. I mark the position of the holes in the sensor tip so I can align them on installation. I keep a blank sensor to use as a plug if I just want to check temperature calibration. I have never gotten an oil bath during this process. I want to always leave the refrigerant side positive as oil out is a lot better then air and moisture in, can I get an Amen on that.-Geo

Once in a while everything falls into place and I am able to move forward, most of the time it just falls all over the place and I can't go anywhere-GEO

Cowpoke- I generally leave just a little (2-4) pounds of pressure and have a new sensor already made up (compression ring on the sensor) so I can pull the old sensor out and push the new sensor in. I mark the position of the holes in the sensor tip so I can align them on installation. I keep a blank sensor to use as a plug if I just want to check temperature calibration. I have never gotten an oil bath during this process. I want to always leave the refrigerant side positive as oil out is a lot better then air and moisture in, can I get an Amen on that.-Geo

My vote is a bad sensor. Shut it down and wait. The two sensors should read pretty close. If they dont, replace. When they fail they usually read way off before they open or short.

This is correct

The sensors themselves can be way out of wack and not cause an alarm, if you suspect this, then you should pull the sensors out and let them sit in a cold water bath along with an accurate thermometer.

This idea is out to lunch !!!

There is no reason the chiller can't be pumped down to replace the sensors. Hook up your gauges and have your hand on the disconnect and make sure it doesn't go into a vacuum. It is not necessary to pull the entire charge just to change the sensors. Pump it down to 20 PSI and change them on the fly.

The RTAA is designed in such a way as all the refrigerant can be transferred to either the high or low side as required to perform service . Use the pumpdown feature and with gauges on the chiller and one hand ready to remove the control fuse or remove the emergency stop jumper and install a toggle switch (PULLING DISSCONNECTS ON HIGH AMP EQUIPMENT IS JUST ASKING FOR TROUBLE ) pump her down . Then use your recovery unit to lower the pressure further to 2/3psi then do a quick swap on the sensor . The holes in the sensor have no relavance as far as I have found and Ive changed more than I can remember . Just be sure not to bottom out the sensor in the pipe and DONT OVERTIGHTEN THE SWAGELOCK NUT YOU WILL CRUSH THE SENSOR INTERNALLY . Open all the valves and ur done .

Out to lunch

graham- Then I would have to say the instructors in Pueblo were out to lunch, because when I attended class for RTAA's way back when we were instructed to check a water or refrigerant sensor for accuracy the best way was having both sensors in the same fluid ( and they said water ice bath with an accurate thermometer) followed by an alcohol cleaning to remove residual moisture from the area around the sensor bead. I have no reason to disclaim what you said about the holes in the refrigerant sensor, but again both the school and the SB both specify that the sensors are position sensitive on the suction side and I have no reason to not follow the outlined procedure. This is just my opinion, then again both the school and SB-5 say to cut the sensor leads at the point of installation and wire nut the new sensor to the existing wire and I have never done that either. I always run the complete sensor and wire to the module and make a new termination on the new AMP plug. I don't leave the wire hanging either, I remove the now unused cable and run the new cable along the same frame rails. Let's face it graham we both know what we are doing. Be safe and keep building those cars. -Geo

Once in a while everything falls into place and I am able to move forward, most of the time it just falls all over the place and I can't go anywhere-GEO